In the international patent application WO2009/112346 A1 of this same applicant, an apparatus and a method are described for executing the closure of a knitted tubular article at an axial end thereof, at the end of its production cycle on a circular machine for knitting, hosiery or the like.
Such method consists substantially of removing the article, at the end of its production, from the needles of the machine by way of a pickup device and of transferring the article to a region arranged laterally to the needle cylinder of the machine where there is a handling device, which receives the article from the pickup device and brings together the two flaps of the axial end of the article to be closed, and a sewing head, which performs the joining of these two flaps thus carrying out the closure of the axial end of the article.
The pickup device described in such international patent application and the subject matter of international patent application WO2009/112347 A1 comprises an annular body that can be arranged coaxially around the upper end of the needle cylinder of a single-cylinder circular machine for knitting or for hosiery and which supports, inside radial grooves, pickup elements that are moveable on command radially and are each engageable, by way of the end thereof directed toward the axis of the annular body, with the shank of a needle of the machine, below the latch, so as to receive in such end, which is barb-shaped with the point directed upward, the last loop of knitting of the article formed by such needle when this is pushed downward below the latch. The subsequent movement of the pickup device upward causes the closure of the latches on the head of the needles and the disengagement of the article from the needles of the machine.
In order to carry out the picking up of the article from the needles of the machine by way of the pickup device of the type described in the international patent applications cited above, it is necessary that the needles of the machine be lifted in the “drop stitch” position and that the last row of knitting formed be held in the heads of the needles without passing below the latches of the needles.
Theoretically, the pickup device described above can also be used for carrying out the picking up of the article from double-cylinder circular machines, by arranging the article inside the lower needle cylinder and bringing the loops of the last row of knitting in the upper head of the needles that are arranged in the lower needle cylinder and which are conveniently lifted so as to permit the engagement of the pickup elements with their shank below the upper latch of those same needles after the upper needle cylinder has been moved away from the lower needle cylinder.
Application of this pickup device to single-cylinder circular machines for hosiery, in order to carry out the automated closure of the toe of socks, has not raised problems, while its application to double-cylinder circular machines for hosiery has been more problematic, mainly owing to the difficulty of successfully positioning the article with the loops of the last row of knitting formed in the upper head of the needles arranged in the lower needle cylinder to the drop stitch position in order to allow a simple and exact coupling with the pickup elements of the pickup device described above below the upper latch of the needles.
In fact, in double-cylinder circular machines for hosiery, the presence of the knockover sinkers, typically curved, opposes the lifting of the article together with the lifting of the needles to the drop stitch position in order to safely prevent the loops of the last row of knitting from passing below the upper latch of the needles arranged in the lower needle cylinder.
In double-cylinder circular machines for hosiery, differently from single-cylinder circular machines for hosiery, the knockover sinkers are driven by actuation cams that are fixed to a supporting element that is arranged inside the lower needle cylinder and which is integral with the supporting structure of the machine as regards the rotation movement about the axis of the lower needle cylinder, not considering oscillations of reduced extent in order to anticipate or retard their intervention on the knockover sinkers. These actuation cams define a path within which a heel of the knockover sinkers, also referred to hereinbelow as “sinkers” for the sake of simplicity, engages, and such path is contoured so as to cyclically cause, by virtue of the rotation of the sinkers together with the lower needle cylinder about its own axis with respect to the supporting structure and therefore to the actuation cams of the sinkers, an approach and a distancing of the beak of each sinker with respect to the axis of the lower needle cylinder so as to cooperate with the contiguous needles in the forming of the knitting. The path defined by the actuation cams of the sinkers is such as to cause a distancing of the beak of the sinkers from the axis of the lower needle cylinder at each feed or drop of the machine and such as to cause an approach of the beak of the sinkers to the axis of the lower needle cylinder in the remaining part of the rotation of the lower needle cylinder about its own axis. For this reason, at the end of the forming of the last row of knitting of the article, the sinkers are engaged with the last row of knitting, except for the area at each feed or drop of the machine. This engagement of the sinkers with much of the last row of knitting of the article produced prevents the lifting of the article together with the needles of the machine in order to bring the needles of the machine to the drop stitch position and maintain or bring the loops of the last row of knitting formed to the upper head of the needles.
In international patent application WO2013/041268 A1 of this same applicant, a method is proposed which can solve this problem.
Such method, in the course of time, has been shown to be susceptible of improvements which are aimed mainly at simplifying the implementation of the machine.
The aim of the present invention is in fact to devise a method for preparing a tubular article of the type of a sock or the like for automated pickup at the end of its forming on a double cylinder circular machine with at least one feed or drop, which is capable of solving the above mentioned problem by using a double cylinder circular machine that is simpler, both to make and to operate, with respect to conventional machines, in particular simpler with respect to the machine illustrated in international patent application WO2013/041268 A1.
Within this aim, an object of the invention is to provide a double cylinder circular machine that is capable of executing the method according to the invention and which offers appreciable simplifications with respect to conventional machines, in particular with respect to the machine illustrated in international patent application WO2013/041268 A1.
Another object of the invention is to provide a method and a machine that make it possible to use, in order to carry out the automated removal of the article from the machine that produced it and transfer it to a station in which the closure is carried out of one axial end of that article, a pickup device provided with pickup elements which are engageable with the shank of the needles below the upper latch of the needles, in particular of the type described in international patent applications WO2009/112346 A1 and WO2009/112347 A1.
A further object of the invention is to provide a method and a machine that make it possible to perform the picking up of the article from the machine at the end of its production extremely precisely.
A further object of the invention is to provide a method and a machine that make it possible to perform the picking up of the article from the machine at the end of its production in a time that does not excessively penalize the production potential of the machine.